Plant Answers

Weekly Express-News Article
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
Saturday, September 22, 2007

“Fall Lawn Activities”

Because of our wonderful rains and mild temperatures lawns are generally in good shape. The autumn is a key time of the year for activities that are important in keeping the lawn healthy and attractive.

The first activity that is essential is to resist the urge to try and keep the grass as lush as it was all summer. Autumn is brown patch time. The fungus makes circles of killed grass beginning in low spots or other areas that stay damp. The best preventive tactic is to keep the lawn on the dry side. Reduce autumn watering to every ten days if you irrigate every seven days normally. Never water more than once a week in the fall if you want to prevent brown patch.

If the weather does not cooperate and we receive excessive rain, brown patch may develop despite your conservative irrigation practices. In that case the fungicides Turfcide and Fung-Away seem to work well at stopping the disease. Repair of the dead areas may not occur until next spring.

Many lawn experts think the fall fertilization is the most important application of the year. It isn’t the most important fertilization because of its contribution to fall greenness and lushness, it is important because it helps the lawn survive cold winter weather and make a fast start in the spring.

In the autumn the days are getting shorter and the lawn is changing its internal chemistry. Instead of using available nutrients for growth, the grass is reorganizing its nutrients to prepare the plants for cold weather and for a fast growth start next spring. That is why some turf specialists feel that the fall fertilization is the most important of the year. Apply about one pound of nitrogen per 1,000 spare feet for efficient fall fertilization. That translates to about seven pounds of the typical winterizer fertilizer with a formula of 15-5-10 or 18-6-12. The bag will usually also tell you the setting on your fertilizer spreader to achieve the one pound target. It is usually the lowest or second lowest setting.

Every brand has a “winterizer” formula fertilizer. The nitrogen is released faster in a “winterizer” fertilizer than the slow release fertilizer that is used in the spring (May 1). If you have left over slow release fertilizer from the spring it is all right to use it up on the lawn. The other option is to use it in your vegetable garden or for cool weather annuals; October is the time to plant them.

The rains have contributed to attractive lawns this summer; they have also encouraged weed growth. Crab grass, purslane, spurge, and other summer weeds will decline as temperatures cool, but a new crop of winter weeds will take their place. Bedstraw, dandelions, annual bluegrass, thistle, rye grass, and rescue grass will be germinating as soon as the first cool spell moves in. It is not too late to prevent the germination for most winter annual weeds by applying a pre-emergent herbicide. These herbicides, when applied as required on the label, provide a barrier that prevents seed germination. The barrier lasts two – four months depending on the product. Two that work well are Amaze for grassy weeds and Portrait for broadleaf weeds.

Do not use pre-emergent herbicides where you want wildflowers to grow. The materials stop desirable seeds from germinating just as well as they do weeds.

Every year I receive questions about the desirability of keeping the lawn green all winter with rye grass. Golf courses do it, and the grounds can be striking as a green oasis in a drab winter landscape. Planting rye really only works on a Bermuda grass lawn. St. Augustine and zoysia are too thick for effective rye culture and they noticeably decline after just a few years of rye culture. Planting winter rye is a kiss of death for buffalo grass. After one year of winter rye culture you can expect the buffalo grass to have extensive dead areas. Even Bermuda grass is stressed by the winter lawn, but less significantly.

My advice is to use winter rye as an erosion control on a new lawn area in the winter if sod for your permanent lawn is not available, but otherwise concentrate on making the permanent lawn healthy and attractive.